Topic: Rebuilding Top End CB750 (Updated 2/27/13)

[NewOldSchool]

I dropped off my cylinder block and head at a local machine shop today.

It kind of happened by chance, I had called a few shops in my area and all are located on the same stretch of road in my city zoned for industrial biz.

I was driving down the street looking for a specific shop and decided to stop at a random one I hadn't spoken with previously. I walk in the front door and immediately notice a fresh cylinder head from a CB750 and a bored cylinder block sitting on a box of Wiseco 836 pistons waiting for their owners. Looks like I stumbled upon the right place!

So I'm getting a fresh hone on the cylinders (stock bore) and getting them media blasted. The head is being blasted, surfaced, new  valve stems from APE and a valve job.

I'll post picks when I get the parts back! (They said only 4 or 5 days!)

[NewOldSchool]

APE is in Rosamond, is that near you?
http://cbrzone.com/sohc.html
Course people ship stuff all over the world these days.
They would do the whole 9 yards, but you could ask them for something less ala carte.

Updates!

I found a local machine shop that has honed and glass beaded my cylinder block as well as glass beaded, surfaced, installed new APE guides, ground seats, and lapped in the valves all for $415.

No I need to mask them off and paint them. Any prep tips, paint recommendations?

[lucky]

I have finally gotten the head off and disassembled to the point where only the valves remain and have two questions:

I did a leak test by flipping the head upside down and filling the combustion chambers with fuel. Sure enough fuel slowly dripped out of the number 2 cylinder exhaust valve over a 30 min period. The rest sealed flawlessly.

First:

My plan is to take each valve one by one and lap them at home. I know the cheap and easy way is to slip fuel line over the end of the valve and put the other end of the line over an extension in the chuck of a drill and slowly turn them in the seat with lapping compound. I have also heard to never do this because it could wear the guides so which method do you recommend?

Second:

When I go to reassemble the top end I have heard two ways to install the head and base gaskets. Either dry or sprayed with copper compound. Which do you all recommend? ( I have the standard cycle x gasket kit)

Sorry double post.

[lucky]

Is this still serviceable?

The teeth are long gone, but they roll freely and aren't falling apart.

Are you kidding?

Look in your oil sump for all those little chunks
 of rubber going through your oil galleys.

That tensioner is 33 year old garbage.

[NewOldSchool]

Haha yea double posted, couldn't re-find this thread at one point.

I ordered a new roller already and I dropped the oil sump when I first bought the bike 2 years ago, again during this rebuild. No chunks either time and the screen was clean.

[killersoundz]

Is this still serviceable?

The teeth are long gone, but they roll freely and aren't falling apart.

I won't bs. My tensioner looked worse than this and I reused it. My motor seems to run fine thus far and the tensioner is doing it's job. keep that oil changed

[ncstatecamp]

More great news, It seams 1 or 2 of my valve guides are worn, I checked them with a micrometer and they are outside of Honda's spec...

I see cycle X has a "Rev Kit" that comes with guides, valves, beehive springs, retainers, and a CX1 cam.

Any experience with this kit or know anything about that cam?

If you find out a review lemme know, might need this too

[lucky]

Is this still serviceable?

The teeth are long gone, but they roll freely and aren't falling apart.

I won't bs. My tensioner looked worse than this and I reused it. My motor seems to run fine thus far and the tensioner is doing it's job. keep that oil changed

I hope you don't come back to the forum in a month and report Killersoundz!!! HHahhahahahha

I hope you are learning.

[lucky]

Maybe I shouldn't have said cheap and easy haha... I am going to carefully take my time and do it right, with all other valves but one sealing flawlessly and compression testing good before I disassembled everything I was going for more of a clean up and fresh gasket job than a total head rebuild.

I'm on a tight budget and just wanted to stop the leaky head issue. You should see how CLEAN this engine is inside, the cam and bearing surfaces look almost new and its the first time I believe this motor has ever been apart! (31,000 miles)

This is typical for a motorcycle engine. They are much cleaner than used car engines inside in general.

[NewOldSchool]

Here are some pics of the head with new APE guides, and the honed cylinders. They decked the head and skimmed the top of the cylinder block too so they are perfectly clean and flat. I still need to paint them.

More good news, I won a set of MC rings on ebay for 45 bucks today!

Sorry for the poor quality cell phone pics.

[NewOldSchool]

I got a set of NOS MC piston rings that come with the one piece oil control ring.

In the box there is the top, 2nd, oil ring and a hexagonal piece that looks to me like it would have something to do with the oil control ring.

Where do I install the thin octagonal ring in the ring set? It does not fit in the groove of the oil ring so I'm a bit lost.



Sorry for double post lost my own thread again!

[NewOldSchool]

Alright, the bike is 100% back together and running amazing, but I am paranoid about making sure oil is getting to the top end. I start the bike and as it runs oil will shoot out of the front (exhaust side) tappet adjustment holes (both left and right) if I remove one of the tappet adjustment covers. When I take off a rearward facing (intake side) tappet cover, there is a bit of mist, but no jet of oil shooting out.

Does this sound correct?